


Silent Night, Naughty Night

by rehliamonster



Category: Undertale (Video Game)
Genre: Dubious Consent, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Tentacles (Undertale), Frottage, M/M, Sanscest - Freeform, Selfcest, Sensitive bones, Somnophilia, Tentacle Sex, Tentacles, bone stimulation, dubcon
Language: English
Status: Completed
Published: 2018-12-26
Updated: 2018-12-26
Packaged: 2019-09-27 12:58:45
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,237
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17162396
Author URL: https://archiveofourown.org/users/rehliamonster/pseuds/rehliamonster
Summary: He initially thought it would’ve much harder to wake up himself without waking Sans, but he hadn’t counted on a key difference between them. They were both heavy sleepers by nature, but… Sans had grown up in a universe that wassafe. Where he’d never had to startle awake at night to defend himself and his bro lest they die to the exp hunters. That simple fact gave Red an edge. He was awake. Sans slept.Perfect.-My gift for the Undertail Secret Santa.The Prompt: Kustard, Somnophilia, preferably with Red getting up to the funny business. If tentacles get involved, that's a bonus.





	Silent Night, Naughty Night

**Author's Note:**

  * For [GhostDaddy](https://archiveofourown.org/users/GhostDaddy/gifts).



> Hey there, GhostDaddy! I was your secret santa this year! You didn't mention in your kustard prompt if you wanted it to be consensual somnophilia or noncon, so I decided to not elaborate and leave it up for interpretation^^ I hope you have fun with your gift! Merry Christmas!

The room was dark and warm when Red woke up, only a faint light falling through the closed curtains. For him it was still enough to see by, easily, but it made him feel superior and sneaky. Some things were best done in darkness. 

Sans laid on his back with his limbs splayed out, his tank top riding up on his spine a little. His fingers were twitching together with his closed sockets; he must have been dreaming. 

Red grinned down at his alternate. 

Cute. 

He initially thought it would’ve much harder to wake up himself without waking Sans, but he hadn’t counted on a key difference between them. They were both heavy sleepers by nature, but… Sans had grown up in a universe that was _safe_. Where he’d never had to startle awake at night to defend himself and his bro lest they die to the exp hunters. That simple fact gave Red an edge. He was awake. Sans slept. 

Perfect. 

He leaned forwards, taking in the other while he wondered where and how to begin. Sans was small and stocky, his bones sturdy, but without his hoodie he lost a lot of bulk. Just like Red did, although a hard life of many fights had still left Red stronger and thicker. He liked that, looking down at the other and feeling bigger and in control. 

Sans couldn’t do anything. 

As long as Red was careful not to wake him, he would be entirely at Red’s mercy. 

With a wide grin, he reached out and scraped the tips of his sharp phalanges lightly over Sans’ spine. A testing little motion. The pale bone flushed ever so slightly blue as he caressed it, but Sans himself didn’t even react, his breathing still even and deep, undisturbed. 

“Sweet,” Red laughed, deliberately keeping his voice low. 

He could already feel himself heating up from the anticipation, magic pooling in his mouth and on his pelvis. With every teasing stroke of his phalanges against Sans’ spine, the initially faint colour there got darker as well, the magic of his alternate reacting to Red’s careful motions. Soon, the whole spinal column was flushed in blue, warm and vibrant. 

It looked deliciously appealing and so Red indulged, leaning forwards to lick a stripe over the individual disks, lapping between them where the magic of his tongue and the magic on the spine crackled against each other. 

A faint grunt could be heard from above him. 

Red sat up again, watching Sans’ face. 

Still smooth and calm. Only his breathing wasn’t quite as even anymore. Then again, neither was Red’s. Time to get this show really going. 

With a deep chuckle, he allowed his stirring magic to do what it was itching to do and curl outwards. His cock appeared first, naturally thick and already leaking, but it didn’t stay at just that today. From his ribcage erupted a set of tentacles, as thick as his arms and almost twice as long, slick and smooth and flexible. They reached forwards immediately as soon as he summoned them, as desperate to get on Sans as Red himself was. Even though they could have a bit of their own mind, they still ultimately reacted to his thoughts. 

And he wanted Sans. 

The tentacles began to wind their way underneath Sans’ clothes. Red could feel the sensation of the fabric on them, every shift felt like a gentle caress. The tentacles also helped to shift Sans, several of them always moving in tandem to ensure the sleeping skeleton wouldn’t be moved too abruptly. Soon enough, Sans was laid bare in front of Red, many points of his body flushed an appealing blue at this point. The soft touches of the tentacles seemed to have had a rousing effect… 

Seeing Sans like that only heightened Red’s lust, but also his amusement. 

Sans was so helpless, being asleep like this while Red manhandled him into whatever position he liked… 

Red’s grin at this point was more than fiendish. 

He wrapped his hands around the lowest of Sans’ ribs, putting no pressure on the grab for now. Just touching, holding on. His tentacles were busy finding their own spots to work with, sneaking into the pelvis and the inside of the ribcage, winding through tibia and fibula, through ulna and radius, cradling Sans’ skull. 

Red was everywhere on Sans and around him, leaving the other no escape even if he did wake up. 

Sans remained fast asleep though. 

With an almost disbelieving laugh, Red began to move. His tentacles squeezed the bones gently and in rhythmically, moving along with Red’s intent. Red himself was humping Sans’ pelvis, dragging his fat cock against the rapidly warming bone. Not much longer, Red thought. 

“c’mon,” he whispered, his voice sounding rough and breathless already. “make me something nice to fuck.” 

Another laugh escaped him when shortly after, the magic on Sans’ pelvis coalesced and formed a cock as well. So obedient. It looked almost exactly like Red’s did, apart from the fact that it had a softer texture, the magic less sharp and defined. He clearly used it less. 

Somehow that only made it more appealing. 

Red began to rut against him in earnest, the lengths of their cocks dragging against each other, the precome that was leaking from their tips easing the way. 

“fuck yeah…” Red groaned, allowing his skull to fall back as he lost himself in the sensation. 

This was it. He’d been so hot for this all day and now he finally got to indulge. He could feel the soft surface of Sans’ cock against his own, the friction and heat as he moved, and from his squirming tentacles he felt the flushed bone, magic tingling against his appendages as Sans’ body reacted more and more to the stimulation. 

His pace was getting faster and faster, and Red would have loved to stay like this, but he needed to look, to _see_ what he was doing. 

He needed to see Sans’ face, blushing by now and with his mouth partially open, breathing hard and fast. 

He needed to see the little twitches Sans’ body made in reaction to the overwhelming amount of stimulation it received. 

He needed to see how Sans subconsciously moved against him, completely unaware of what he was doing. 

Sans, completely helpless, for Red to enjoy. 

The thought in combination with the view finally sent him over the edge, his body locking up as he found his release. His sockets scrunched shut and his tentacles tightened their squeeze around Sans’ bones. A deep groan echoed through the room that didn’t come from Red alone, two voices that sounded almost the same mingling together. 

Red needed a moment to catch his breath again, the rush of his organs taking a bit to recede. 

“...sans?” he asked. Red was still panting, but he was watching Sans like a hawk. 

No reply. 

Sans’ brow bones were drawn together, his face blue and his mouth still hung open. He squirmed a little, now. The stains of cum on his ribcage proved beyond doubt that he’d come as well, just like Red had. 

But… 

Sans was still deeply asleep. 

“i can’t believe you,” Red cackled. “you lazy little shit.” 

Well, he supposed that meant it was time to find out what would last longer, he thought as he began to move again.

Red’s stamina, or Sans’ ability to stay asleep...


End file.
